Correct hashtag warning (mastodon#22827)

Posts with any visibility setting that is not 'Public' are prevented
from being listed under any hashtag.

app/javascript/mastodon/locales/en.json

@@ -128,7 +128,7 @@
   "compose.language.search": "Search languages...",
   "compose_form.direct_message_warning_learn_more": "Learn more",
   "compose_form.encryption_warning": "Posts on Mastodon are not end-to-end encrypted. Do not share any sensitive information over Mastodon.",
-  "compose_form.hashtag_warning": "This post won't be listed under any hashtag as it is unlisted. Only public posts can be searched by hashtag.",
+  "compose_form.hashtag_warning": "This post won't be listed under any hashtag as it is not public. Only public posts can be searched by hashtag.",
   "compose_form.lock_disclaimer": "Your account is not {locked}. Anyone can follow you to view your follower-only posts.",
   "compose_form.lock_disclaimer.lock": "locked",
   "compose_form.placeholder": "What's on your mind?",